The present invention relates to a torque converter with a rotary oscillation damper, in particular for a motor vehicle.
The state of the art includes torque converters in a multitude of configurations in which rotary oscillation dampers (hereinafter referred to as dampers, for short) are an integral part. In the torque-transfer connection from a combustion engine to the input shaft of a transmission, the torque is transmitted through at least one input part of the damper by way of springs to an output part. In order to retain the springs securely in place at all times, the at least one input part and the output part are arranged intimately adjacent to each other, and as a result there is a considerable amount of friction between these parts.
In order to achieve favorable damping properties in a torque-converter damper, the hysteresis should be as small as possible and, most of all, it should be uniform.
In the common understanding, the term hysteresis means a deviation of the characteristic curve that represents torque as a function of the angle of rotation where, as a result of friction, the characteristic curve does not pass through the origin of the torque/angle coordinate system. In other words, due to frictional forces or torques, the torque/angle graph (under the assumption of a constant frictional force or torque) for one sense of rotation is shifted upwards, parallel to a “hypothetical torque/angle characteristic” passing through the origin, while for the opposite sense of rotation, the torque/angle graph is shifted downwards. As a result, there is a discontinuous jump in the torque at the reversal of the sense of rotation. As a further drawback, the torque/angle characteristic lacks a reversible, linear behavior around the zero point.
As a further negative factor, the hysteresis (even in cases where it is small) is difficult to control over the angular range of the damper and in its behavior over long periods of time.